Weighing scale check link



April 4, 1953 s. WILLIAMS 2,634,966

WEIGHING SCALE CHECK LINK Filed July 2'7. 1948 2 SHEETS-SHEET l F 9 I Y JNVENTOR.

Lawrence .5. W/'///'ams April 14, 1953 s. WILLIAMS WEIGHING SCALE CHECK LINK 2 SHEETS-SHEET 2 Filed July 27, 1948 INVENTOR. Lawrence .5 W/l/iams BY I,

I I l l/ a I I I ATTORNEYS Patented Apr. 14, 1 953 WEIGHING SCALE CHECK LINK Lawrence S. Williams, Toledo, Ohio, assi'gnor to Toledo Scale Company, Toledo, Ohio, a corporation of New Jersey Application July 27, 1948, Serial No. 40.883

3. Claims. 1

This invention relates towelghing scale check links and in particular to an improved structure that is easy to manufacture and to adjust when installed in a scale.

Any weighing scales having a platterlocated above a lever and supported from a pair of aligned knife edges or a single extended knifeedge of the lever require a check link to keep the platter in position. In order that the scale shall weigh accurately for all positions of the load on the platter, it is necessary that the efiective length of the check link shall be exactly equal to the distance between the fulcrum and load knife edges of'the lever and that the check link be exactly parallel to the pivot line of the lever for all positions occupied by the lever during normal weighing operation.

It has been customary, in order to secure the required accuracy, to employ opposed knife edges and bearings at each end of the check link for pivotally connecting the link to the frame of thescale and to the load receiver that it is to stabilize. The opposed knife edges and bearings at. each end of the check link provide a pivoting axis that is able to transmit either a. tension or a compression force acting along the length of the check link. The force may be tension or compression depending upon the position of the load on the platter;

Such a construction employing knife edges and bearings. is expensive to manufacture and .diffi cult to install and adjust in a scale. The. dim-- culty arises because itis necessary that the pivoting axis provided by the opposed knife edges shall be parallel to the pivoting axis of. the lever as well as. being located a precise distance from the pivoting axis of the lever.

The principal object of this invention is to provide a simple, easily constructed check link that has extremely low friction and that is easy to adjust.

Another object of the invention is to provide a simple check link in which the force, whether tension or compression, is'transmitted along the same line in the check link.

Another object is to provide a simplified method of manufacture of the improved check link.

Other objects and advantages are apparent from they following description in which refer,- ence is made to the accompanying drawings.

According to the invention, the improved check link comprises a strip of flat stock which at each end has atransverse bore the peripheryof which is hardened to form the bearing race. for a plurality of ball bearings, side plates attached to the strip of stock to hold the balls in position, and cone-pointed screws that loosely engage opposite sides of one of the side plates of the check link one of which screws has a cylindrical portion forming the inner race for the balls enclosed within the cylindrical bore. The invention also includes an improved method 0! manufacturing the improved check link.

The accompanying figures illustrate the installation of the improved check link in a weighing scale and also the successive steps in the manufacture-of the check link.

In the drawings:

Figure I is a side elevation, with parts broken awayand otherparts shown in section, of a, scale employing the improved check link.

Figure His an enlarged perspective view of the improved check link and fragmentsof the structure connected thereto.

Figure III is a fragmentary vertical section taken through one end of the improved check link and the connected structure.

Figures IV, V, VI and VII illustrate the check link during successive stages of its manufacture.

These specific figures and the accompanying description are intended merely to illustrate the invention but not to impose limitations on the claims.

A weighing, scale incorporating a check link according to the invention comprises a base I in which are fitted V-bearings 2 to receive fulcrum knife edges of a weighing lever 3. A spider 4, havinglaterallyextending arms 5 containing vbearings 6 resting. on load knife edges I of the lever 3, has uprights 8 the upper ends of which carry a shield 9 and a. load receiving platter l0. Forces applied to the load receiving platter I0 are transmitted to. the lever 3 and through the lever to its power pivot H which is operatively connected to a load counterbalancing mechanism contained within a column [2 erected from the rear portion of the. base I of the scale. The load counterbalancing mechanism, which forms no part of the instant invention, is not shown in the drawings. The load counterhalancing mechanism is operatively connected through a rack rod 13 and rack I4 to a pinion 15 mounted on the shaft of a drum. chart IB. The chart I6 is enclosed. within asubstantially cylindrical housing ll surmounting the column 12. Magnifying glasses mounted within a viewing hood I8 provide enlarged images of weight or computed amount indicia. that are printed or otherwise marked on the cylindrical chart I6. I

The platter, I0 is held in operative relation to the remainder of the scale bya. check link I9 one end of which is pivotally connected to the upper end of an upright erected from the central portion of the spider 4 and the other end of which is pivotally mounted in a yoke 21 forming the upper end of a threaded stem 22. The threaded stem is held in adjusted vertical position by lock nuts 23 and 24 that are threaded on the stem 22 and that engage the upper and lower surfaces of a boss 25 forming the upper end of a pedestal 26 erected from the base I of the scale.

The threaded stem 22 has a flat 27 cut in one .i

side, which flat is engaged by the inner end of a set screw 28 threaded through the side of the The check link 19, formed from 'a'flat strip of e The fiat 27 and set screw 26 serve to material, has a bore 29 at each end in whichbores ,3

a plurality of bearing balls tll are fitted. Retaining plates 31 and 32 attached to the sides of the check link i9 serve to hold theballs ea in position. Since the thickness of the check link 19,

its dimension along the length of the bores cut in its ends, is slightly greater than the diameter of one ofthe balls, it follows that the balls are loosely held and free to revolve as may be necesv sary in providing a frictionless pivotal connection. The plates 32, one at each end of the check link [9, are perforated thus providing holes 33 a that are coaxial with respect to the bores 29 and somewhat larger in diameter than a circle that is tangent to the innermost points of the balls 30.

The upper end of the upright 28 of the spider 4 is bifurcated to provide arms 34 that are similar in function to legs 35 and 36 of the yoke 21.

vElach of the pivotalconnections between the check link i9 and the yoke 2i or' the upright 26 comprises a first cone-pointed screw 3! the conical tip of which en ages the outermost surface of the plate 3! at a, point that is coaxial with the b9re,29- of;the check link 19. This cone-pointed screw 3'! prevents rubbing contact between the side of the plate (H and the adjacent surface of the leg 36.

cal shank 39,0f the-screw 38 forms the inner race for the bearingballs 36.. The clearance between the cone points of the screws 37 and 38 and hence the side play of the check link is adjusted by turning the screw 36 in or out and the screw is held in adjusted position by a lock nut ii that is tightened against the side of the yoke 2 l.

A small amount of clearance must be provided to prevent binding between the check link IS, the bearing balls 32, and the cylindrical shank 39 of the screw 38. This binding would be aggravated if the check link L) were in neutral or unstable equilibrium so that it would tend to tip over sideways instead of remaining upright as shown in the drawings. This tendency to tip sideways may be minimized by lightening the upper half of the check link 19 by drilling therethrough a series of holes 22. Similar results can be obtained by adding weight to the lower half of the check link or by locating the bores 29 non-symmetrically with respect to the horizontal centerline of the check link so that the greater portion of the check link lies below a line connecting the centers of the bores.

The peripheries of the bores 29 and the shanks 39 of the screws 38 are hardened and ground to minimiz the friction that would otherwise result if the balls 36 slightly indented the surfaces with which they cooperate.

This structure is ideally suited for use in a check link because the distance between the bores 29 at the ends of the check link may be precisely determined during the machining ofthe check link so that this distance corresponds precisely with the pivot distance of the lever 3. The parallel condition between the check link and the lever is obtained by adjusting the stem 22 vertically'through the boss 25 of the pedestal 26. Further adjustments are not required because the line of 7 action of the force transmitted through the check link i9 is in the plane of the balls Bil at'each'e'nd of the check link. Since these balls are in line, the efiective distance as well as the parallelism between the line of force and the pivot line of the lever isindependent of slight variations or deviations of the screws 36' from exact parallelism with the fulcrum or load pivot lines of the lever 3. As a result, this check link, evenif its support is not exactly in line, provides satisfactory performance when used in a weighing scale and because of the elimination of several adjustments is considerably easier to install and adjust.

The various steps in the manufacture of the improved check link are illustrated in Figures IV to VII inclusive. Thus in Figure IV the holes 42 have been drilled in the check link bar l9 and the bores 28 have been drilled and their edges lightly beveled. Furthermore, the ends of the bar I9 including the peripheries of the bores 29 have been heat treated to harden the bores 29 as required for satisfactory operation with the balls. In addition, the bores 29 may at this stage be ground if desired to still further improve the surface finish.

As shown in Figure V, the side plates 32 have been added as by spot welding along the edge of one end only of the plates 32 so that the plates are free to spring outwardlyv away from the check link bar is at their outermost ends. Also at this stage the holes 33 are drilled or otherwise cut in the side plates 32. The fixture or jig for locating the holes 33 may, and preferably does, employ.

the periphery of the bores 29 as a reference surface in locating the holes 63. paratively simple to maintain the exact coaxial relationship between the holes 33 and the bores 29 without the necessity of using expensive locating equipment.

After the holes 33 have been drilled the other: side plates 3! are attached to the ends of the check link is again by welding or other suitable attaching means employed at one end only ofeach of the side plates. This step is illustrated at the left end of the bar as shown in Figure VI.

the cylindrical shank 39 on the end of the screw 38 is made slightly larger than the diameter of one of the balls as and the diameter of the bore 29 is made slightly larger than three times the diameter of a ball. Thus, six balls will substantially fill each of the bores 29.

Thus it is com Since the balls" 36 are. introducedfrom the center of the ring'and have to pass to the outside and since there is insufficient clearance (if they are all retained in the same plane) to permit the sixth ball to move from the center of the bore 29 to its allotted space in the ring, the side plates 31 and 32 are sprung away from the check link bar I9 far enough to allow the first five balls to move out of the common plane and thus provide clearance to permit the sixth ball to slip into place in the ring.

After the sixth ball is in place and the plates 3! and 32 have sprung back to their original position, the plates are welded or otherwise secured at their previously free ends to prevent such springing action when the check link is in use. This final welding operation completes the manufacture or" a check link and it is then ready for installation in the weighing scale.

Th simplicity of manufacture of this check link, as compared to the manufacture of conventional check links, is readily apparent when one considers that the only precise dimensions to be maintained are the spacing and diameters of the bores 29 and the diameters of the cylindrical shanks 39 of the screws 38. The location of the holes 33 is easily accomplished because of the adjacent reference surfaces-the peripheries of the bores 29-and the remaining operations such as drilling the holes 42 and welding the plates 31 and 32 do not contribute to the dimensions of the check link and, therefore, need not be precision operations.

Various modifications may be made in the improved check link without departing from the spirit and scope of the invention.

Havin described the invention, I claim:

1. In a weighing scale, a check link comprising a fiat bar having a transverse circular bore at each end, a flat plate attached to each side at each end of the bar for closing the ends of the bores, one of the plates at each end of the bar having an opening coaxial with and smaller than the bore, and a plurality of balls disposed in a circle contained within each bore, the balls having diameters slightly less than the thickness of the flat bar between the fiat plates.

2. In a weighing scale, a check link comprising a flat bar having a transverse circular bore at each end the diameter of which bore is approximately three times the thickness of the bar, a flat plate aifixed to each side of each end of the bar to close the ends of the bores, and a plurality of balls contained within each bore, each of the balls havin a diameter slightly less than the thickness of the bar between the plates, one only of the plates at each end 01 the bar having a hole the diameter of which is greater than the diameter but less than twice the diameter of a ball.

3. In a weighing scale, a check link assembly comprising a first yoke supported from the frame of the scale, a second yoke attached to the part to be guided, a check link bar having at each end a transverse bore, a plurality of balls contained in each bore, a pair of plates one of which is perforated attached to each end of the bar for retaining the balls, a pin carried in each yoke and adapted to engage the balls, and a second pin carried in each yoke in axial alignment with the first pin, said pins being pointed to loosely engage the sides of the unperforated plate to retain the check link bar in position.

LAWRENCE S. WILLIAMS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 869,135 Burbank Oct. 22, 1907 1,686,732 Cheetham Oct. 9, 1928 1,810,093 Timson June 16, 1931 1,834,938 Conard Dec. 8, 1931 1,837,601 Wetzel Dec. 22, 1931 1,899,436 Fletcher Feb. 28, 1933 1,941,849 Meyers et al. Jan. 2', 1934 2,0 3,961 Hurt Sept. 10, 1935 2,090,288 Eschenbacher et al. Aug. 1'7, 1937 2,144,845 Kniesche Jan. 24, 1939 2,387,202 Williams Oct. 16, 1945 2,464,511 James Mar. 1'5, 1949 2,545,908 Weckerly Mar. 20, 1951 

